Retrievable well tool



y 1970 D. E. YOUNG 3,509,940

RETRIEVABLE WELL TOOL Filed Oct. 30, 1968 .5 Sheets-Sheet 2 FIG. 20

INVENTOR. DAVID E. YOUNG his A TTOR/VEYS May 5, 1970 D. E. YOUNG 3,509,940

RETRIEVABLE WELL TOOL Filed Oct. 50, 1968 5 Sheets-Sheet 4 his ATTORNEYS y 1970 D. E. YOUNG 3,509,940

RETRIEVABLE WELL TOOL Filed Oct. 50, 1968 v5 Sheets-Sheet 5 I I T F/6.6 n2 JlI l I n5 Ilb. 1 1 V i I --H6a A l INVENTOR.

DAVID E. YOUNG his ATTORNEYS United States Patent 3,509,940 RETRIEVABLE WELL TOOL David E. Young, Beilaire, Tex., assignor to Schlumberger Technology Corporation, Houston, Tex., a corporation of Texas Filed Oct. 30, 1968, Ser. No. 771,846 Int. Cl. E21b 23/ US. Cl. 166121 26 Claims ABSTRACT OF THE DISCLOSURE According to the exemplary embodiment, a retrievable bridge plug of the type adapted to be anchored in a well conduit against both upward and downward movement and to seal the well conduit against passage of fluids in either direction comprises an upper body and a lower body depending from the upper body and arranged for limited sliding movement thereon. The upper body carries an upwardly facing cup-type packing element and the lower body a downwardly facing cup-type packing element. Both bodies have friction drag capability so that they are substantially self-supporting in the well. Slips on the lower body coact with expander surfaces on the upper body to anchor the tool in the conduit, and a control system selectively permits or prevents relative movement of the upper and lower bodies to permit or prevent the setting of the slips. Although the tool has only a single expander and set of slips, it is capable of being anchored against movement in either direction by providing a hydraulically developed downward reaction force on the expander to react against differential pressure tending to push the lower body and slips upwardly. Valves operated by the control system are opened to bypass fluids and closed to bridge the conduit.

BACKGROUND OF THE INVENTION This invention relates to a well tool of the type which is used to seal ofi selected zones in a well conduit against fluid passage and which is adapted to be anchored in the well conduit against movement in either direction, released from anchored and sealed condition and moved in the conduit to different positions and ultimately retrieved.

In many remedial, stimulation and production operations performed in wells, such as fracturing, acidizing, squeeze cementing and the like, special tools are used to isolate selected portions of the well conduit. For example, many operations employ a tool known as a bridge plug to seal or pack off the entire cross section to prevent fluid communication between the zones above and below the tool. Another type of tool, commonly called a well packer, is used to isolate an annular space between the casing and a tubing string running up through the casing to the well surface from a zone below the well packer. There are many forms of bridge plugs and well packers in service in the oil industry. In these operations, the tools are often of the so-called retrievable type which are characterized by their ability to be lowered into the well, set in anchored and sealed position While the operation is carried out, released after the operation is completed and perhaps shifted to another location for another operation, and ultimately recovered from the well.

In some types of remedial, stimulation and production operations, it is necessary only for the tool to be capable of holding a differential pressure acting in one direction. Commonly, tools of this type are equipped with a single set of anchoring slips and coacting expander surfaces arranged such that the differential pressure held by the tool acts on the expander element to force it toward the slips. This provides a positive wedging action of the exice pander under the slips and ensures that the slips are firmly held in gripping engagement with the conduit, inasmuch as the gripping of the slips with the conduit provides a reaction force for the active force on the expander.

characteristically, slips of the type used in well tools of the usual single acting type operate only when the force tending to set them is imposed through the expander in the direction of the slips. Where the net active force operates on the slips and pushes them toward the expander, there is no reaction force on the expander to prevent it from being moved with the slips.

In many operations it is desirable, and often necessary, to employ a bridge plug or well packer which holds against differential pressures creating forces tending to move the tool either up or down in the conduit. Inasmuch as one slip and expander pair have the characteristics described above of holding in only one direction, many double-acting well tools have two sets of slips and coacting expanders. One set of slips and its expander anchor the tool against upward movement, and the other anchor it against downward movement. Because of the two sets of slips and coacting expanders, the construction of these tools is often quite complicated and certain difficulties in their operation may arise.

A number of designs of double-acting packers and bridge plugs which employ only a single set of slips and a single expander have been proposed and used. Many of these tools operate by mechanically jamming the expander and slips together with a pre-load force, such as that developed by screw threads or in some other fashion so that the tool is anchored as a result of the pre-load forces and is not dependent upon forces developed by differential fluid pressure acting on the tool.

My co-pending US. patent application Ser. No. 703,946 filed Feb. 8, 1968 and the US. patent application of James W. Kisling III, Ser. No. 703,947, filed Feb. 8, 1968, describe and illustrate retrievable bridge slugs which are constructed so as to be anchored in a well conduit against movement in either direction and yet employ only a single set of slips and expanders. Both of these tools have hydraulic systems for generating a reaction force acting on the expander under pressure conditions which create active forces acting on the slips and urging the slips toward the expander. These applications, which are assigned to the assignee of this application, as well as certain other applications also owned by the assignee of this application, disclose novel and improved tools having various features providing important advantages adapting them particularly for use in certain operations and under certain conditions.

SUMMARY OF THE INVENTION There is provided, in accordance with the invention, a retrievable well tool which includes an anchoring structure of the type adapted to anchor the tool against both upward and downward movement in the well. The anchoring mechanism has only one set of slips and an expander which coacts with the slips to anchor the tool against both upward and downward movement in a well conduit. The tool remains set in anchored engagement regardless of a shift in pressure conditions that changes the direction in which the slips are holding, and such a shift in the pressure conditions involves no substantial movement of the sealing and anchoring structure of the tool.

More particularly, a well tool, according to the invention, comprises an upper body and a lower body, the lower body depending from the upper body and mounted on it for limiting longitudinal sliding movement. The upper body carries an upwardly facing cup-type packing element which forms a seal between the upper body and the conduit wall against downward passage of well fluids, and the lower body carries a downwardly facing cup type packing element which forms the seal between it and the conduit against upward passage of well fluids. A set of anchoring slips are mounted on the lower body for movement outwardly into engagement with the conduit wall, and the upper body has expander surfaces positioned to engage the slips and Wedge them outwardly, upon relative upward movement of the lower body, into gripping engagement with the conduit wall. The tool further includes a control arrangement for selectively permitting or preventing movement of the upper body relative to the lower body. A hydraulic system responds to a differential pressure tending to move the lower body upwardly toward the upper body, and therefore to force the slips upwardly toward the expander, by generating a downward reaction force on the expander so that the expander is able to maintain the wedging action required to hold the slips in engagement with the conduit wall.

In a preferred embodiment of the invention, the control system is of a type which is operated solely by longitudinal movements so that the tool can be used with a wire line or cable, as well as with tubing. The control system may comprise an arrangement for developing frictional forces with the wall conduit to render the upper body and lower body self-supporting in the conduit so that they will not shift relative to each other under nor mal conditions. Preferably, the upper and lower bodies carry friction drag elements, such as spring-loaded friction drag shoes. The control system may also include a longitudinally shiftable control element which is arranged to -(l) selectively engage and impose a downward force on the lower body, (2) engage and impose an upward force on the upper body or (3) occupy a neutral position in which relative movement of the upper and lower bodies toward each other is permitted.

The tool according to the invention is lowered into the well by pushing it down using a running-in tool, such as a weighted wire line running tool. The running tool engages the control element and forces it down so that a control element in turn engages the lower body and pushes it down through the well. The upper body is pulled down through the well by the lower body. Similarly, by pulling up on the control element, the upper body is pulled up and drags the lower body up with it. In either case, the upper and lower bodies are relatively separated to a maximum extent and the slips are therefore retracted. In a neutral position, however, the control arrangement permits the upper and lower bodies to be shifted toward each other.

The tool further comprises a passage to bypass fluids, as the tool is run up or down in the well, and the passage has valves operated by the control system to close off the passage when the tool is set.

When the control element is in a neutral condition and the tool is subjected to a higher pressure from above than below, a downward force is exerted on the upper body and shifts it downwardly toward the lower body, and forces the expander surfaces down along the slips to move them outwardly into anchoring engagement with the conduit. Under this condition, namely, a downward force on the expander element wedging it down along the slips, the slips are held more tightly wedged as the downward force is increased, and the slip-expander set operates in the usual manner.

When there is a higher pressure below the tool than above it, the lower body is shifted upwardly, toward to the upper body, and the slips are similarly shifted out into engagement with the well. However, even when the slips engage the well conduit wall, the expander would be relatively free to move upwardly with the slips, if it were not for the hydraulic reaction system, inasmuch as the only forces resisting its movement are the frictional and gravity forces acting on the upper body.

More particularly, the hydraulic reaction system generates a reaction force on the expander, acting down toward the slips, to hold the expander wedged under the slips and comprises a fluid chamber of variable volume defined by formations 0n the upper body and lower body. In a preferred arrangement, the tool is constructed such that the upper end of the lower body is telescopically received in the lower end of the upper body and there are companion shoulders formed on the lower and upper bodies which serve to limit the extent of their movement away from each other. The shoulder formations and companion cylindrical walls in the sliding relationship of the telescopic portions provide the hydraulic chamber. The interior of the chamber is communicated with the zone of the well below the lower packing element. Meanwhile, the exterior of the chamber is in communication with the annular space between the tool and the conduit between the two packing elements. The pressure in this space tends to stay rather close to the pressure above the upper packing element when there is a higher pressure in the zone of the well below the lower packing element, inasmuch as fluid pressure bleeds off past the upwardly facing upper packer element. Accordingly, the interior of the chamber is subject to pressure from below the lower packing element and the exterior of the chamber is subject to pressure above the upper packing element. As a result, a higher pressure within the chamber produces a net downward force on the upper body which serves as a reaction force acting on the expander to hold it down and react against the slips so that the slips are wedged firmly into gripping engagement with the Well conduit wall.

Among the advantages of the tool according to the invention is its relatively short length, which is made possible by having only a single set of slips and coacting expander. Moreover, the tool does not have a unitary central body, which is characteristic of most packers and bridge plugs, so it is relatively lighter in weight than many equivalent tools. The telescopic relationship between the upper and lower bodies, however, makes it desirable to provide a mechanism for preventing the upper and lower bodies from shifting relative to each other when the tool is not falling in a well conduit, such as when it is being transported and, even more importantly, as it is being inserted into the conduit. Accordingly, a further feature of the tool is the provision of a latch mechanism which prevents the upper and lower bodies from shifting relative to each other and holds them in a position in which the slips are retracted. Desirably, the latch mechanism is arranged so that it automatically releases when the tool is inserted into the well.

In a preferred embodiment of the latch mechanism, the lower body, in the region which is telescopically received within the upper body, has a notch formed in its outer wall, and the upper body carries a latch element which has a projection that is received in the notch to provide a detent arrangement. The latch element is pivotably mounted on the upper body adjacent the upper drag shoe, and companion formations on the latch element and the drag shoe engage each other in a manner such that the drag shoe causes the latch element to pivot in a direction to hold the projection in the notch of the lower body when the drag shoe is in its radially outermost position on the body, a position which it will occupy when the drag shoe is not within the well casing. When the tool is inserted into the casing to an extent that the drag shoe enters the casing and is pushed inwardly from its outermost position, the drag shoe is shifted radially inwardly and releases the latch so that relative movement between the upper and the lower bodies is thereafter permitted. At this point, however, the drag shoe on the upper body assumes its functions of supporting the upper body in the 'well conduit so that relative movement does not take place and the tool remains in the unset position for lowering through the conduit.

When the tool is pulled up to move it to another location in the well or to remove it from the well altogether, the latch resumes its locked position as soon as the upper drag block leaves the confinement of the well casing, and shifts outwardly to again engage the latch element and hold the latch element projection in the notch on the lower body.

As mentioned above, the tool may be run with either a tubing string or with a wire line, this versatility constituting an important advantage in that it renders the tool subject to wider use as to types of operations in which it can be used. In either case, an appropriate running-in and retrieving tool may be employed. In certain operations in which the tool is used, sand or mud may accumulate on top of the tool, and retrieving it will require the use of a tubing string in order to circulate to remove the sand or mud. Desirably, the retrieving tool used with tubing will have milling teeth at its lower end, and the tubing string will be rotated to assist in washing down to pick up the tool, Accordingly, it is preferable for the control element of the tool, with which the retrieving tool becomes engaged, to be freely rotatable clockwise (to the right) so that the running tool can be rotated during the washing down operation.

In a preferred embodiment, the tool has a control rod having a transverse member on it which slides in elongated, longitudinal slots in the upper end of the upper body. The part of the upper body in which the slots are formed is desirably a separate piece mounted in a manner affording rotation on the upper body in one direction only and, further, mounted in a substantially fixed position vertically. A clutch device is provided between the main upper body section and the rotatable section so that the rotatable section will turn clockwise relative to the main part of the upper body but is prevented from turning counterclockwise. As will be apparent from the description of the embodiment illustrated in the drawings, rotation of the tubing string and retrieving tool counterclockwise (to the left) is accomplished to release the retrieving tool from the well tool.

DESCRIPTION OF THE DRAWINGS For a better understanding of the invention, reference may be made to the following description of an exemplary embodiment, taken in conjunction with the figures of th accompanying drawings, in which:

FIGS. 1A, 1B and 1C, taken end to end one over the other in the order stated, constitue a half sectional, half elevational side view of the exemplary embodiment of a tool with the parts shown in the position they occupy when the tool is being moved downwardly through a well conduit;

FIGS. 2A, 2B and 2C, taken end to end in the order given, make up a half sectional, half elevational side view of the embodiment with the parts shown in the position they occupy when the tool is anchored in the well conduit;

FIG. 3 is an elevational view, but with certain parts in section, of the embodiment of the tool after it has been partially inserted into a well casing;

FIG. 4 is a detail on a part view relatively larger scale, of the latch mechanism of the tool;

FIG. 5 is a cross-sectional view of the upper end of the upper body showing details of the clutch which permits a rotatable section of the upper body to turn in one direction only relative on the main section of the upper body;

FIG. 6 is a side sectional view of an exemplary running and retrieving tool for use with the tool; and

FIG. 7 is a development of the J-slot of the running and retrieving tool shown in FIG. 6.

DESCRIPTION OF THE EXEMPLARY EMBODIMENT The embodiment of the well tool illustrated in the drawings and described below is a retrievable bridge plug of the type that can be lowered into a well conduit with a suitable running and retrieving tool, disconnected from therunning and retrieving tool at a desired location in the well conduit and, upon a pressure differential across the tool, becomes anchored to the conduit wall against movement either up or down and seals off the conduit against the passage of well fluids in either direction past the tool.

The retrievable bridge plug, as embodied in the version shown in the drawings, comprises an upper generally tubular body 10 and a lower generally tubular body 12, the lower body 12 depending from the lower end of the upper body and arranged for limited sliding movement relative to the upper body. Both the upper and lower bodies 10 and 12, as is well known to those skilled in the art, are made up of a number of pieces threaded or otherwise appropriately connected together, but the several pieces making up the bodies are, for simplicity of illustration, not shown in the drawings. The upper and lower bodies 10 and 12 are prevented from rotating relative to each other by interengaging slot and rib formations 17 (see FIG.

1C) on the lower body and upper body, respectively, the

formations being of sufficient length to allow for the relative longitudinal movement of the bodies.

The major portion of the upper body 10 is constituted by a main section 14, and on the lower end of the upper body (see the top of FIG. 1C) is a set of tapered expander surfaces 16 which coact with a set of slips 18 mounted on the lower body. Above the expander surfaces (see FIG. 1B), the main section 14 of the upper body 10 is formed with circumferentially spaced-apart recesses 20 which receive friction drag blocks 22. The friction drag blocks 22 are urged radially outwardly by springs 24 into an outermost position as established by overhanging flange formations 26 at the longitudinal ends of the recesses 20. Just above the friction drag blocks 22, the inner wall of the body is formed with an enlarged portion 28 so as to define an upwardly facing shoulder 30 and a downwardly facing shoulder 32. As described in more detail below, the enlarged portion 28 receives an enlarged portion of the lower body and enables relative sliding movement of the lower body between predetermined limit positions established by the shoulders 30 and 32.

An upwardly facing cup-type packer element 34 mounted near the upper end of the upper body 10 forms a seal between the well conduit, such as a well casing C, and the upper body to prevent the downward passage of fluids between the casing and the body. However, this type of packing element permits fluid to leak off in an upward direction, should the portion of the annular space between the tool and casing below the packing element tend to have a fluid pressure higher than that above the packing element, such as may occur when the well is swabbed.

As mentioned briefly above, the upper end of the lower body is telescopically received within the lower end of the upper body for limited longitudinal sliding movement. To this end, the upper end of the lower body has an enlarged portion 36 received within the enlarged recess portion 28 on the inner wall of the upper body. A sleeve portion 38 of the lower body extends down through the bore within the lower end of the upper body past the lower end of the upper body to a point where it meets a slip mounting portion 40 which is provided with appropriate slot formations at circumferentially spaced positions to receive companion lugs on the anchoring slips 18. The slips 18 and expander surfaces 16 are dovetailed so that the slips are guided in and out upon relative longitudinal movement of the upper and lower bodies. The companion lug and slot formations on the mounting portion 40 of the lower body and on the lower ends of the slips 18 mount the slips on the lower body while affording radially inward and outward movement.

Just below the slips, the lower body carries drag blocks 42, which may be identical to those used on the upper body and which, therefore, are not described in detail, and mounted near the lower end of the lower body is a downwardly facing cup-type packer element which forms a seal between the lower body and the Well conduit in the well casing C against the upward passage of well fluids.

Both the upper and lower bodies and 12 are hollow so as to afford a central passage 46 through the tool from a point below the lower packing cup 44 to a point above the upper packing cup 34. At the lower end of the passage 46 and below the lower packing element 44 are fluid ports 48, and similar ports 50 are formed in the upper body at a point above the upper packing element 34. Accordingly, well fluids may pass in either direction through the retrievable bridge plug as it is being moved up or down in the casing C. However, the retrievable bridge plug includes a valve arrangement which closes oil the passage 46 so as to bridge the casing C when it is set.

More particularly, the retrievable bridge plug includes a control mechanism which operates the valve arrangement and which also controls the setting and unsetting of the anchoring elements (the slips and expander set). The control mechanism comprises an elongated control mandrel 52 which extends from a point above the upper end of the upper body, where it is provided with a top piece 54, down through the upper part of the upper body and further down into a portion of the lower body. Near the lower end of the control mandrel 52 is an outwardly projecting flange 56 which operates a spring-loaded lower valve element 58.

When the retrievable bridge plug is being pushed downwardly through the casing, the control mandrel is pushed down, and the flange 56 engages the upper end of the valve element 58 and pushes it down against its spring 59, relative to the lower body into a position in which the valve element 58 is unseated from a valve seat 60 formed on the enlarged portion 36 of the lower body (see FIG. 1B). In this position, outwardly extending lugs 62 on the valve element 58 seat on a shoulder 64 on the lower body so that the downward force on the control, mandrel 52 is transmitted through the valve element 58 and into the lower body and pushes the lower body down through the Well casing. In the meantime, well fluids may enter through the lower ports 48 and pass upwardly through the center passage 46 and through the then open valve 48.

At a point on the mandrel 52 somewhat above the flange 60 is a second outwardly extending flange 66 which operates an upper valve element 68 which, like the lower valve element, is carried for sliding movement on and is in sealing relation to the control mandrel 52. When the control mandrel 52 is pushed down, the flange 66 is out of engagement with the upper valve element 68 so that a spring 70 associated with the upper valve element can urge it into sealing relation on an upper valve seat 72 formed on the upper body. However, in the running in or lowering position of the tool illustrated in FIGS. 1A, 1B and 1C, the upward passage of well fluids through the central bore 46 of the tool unseats the upper valve element 68and permits well fluids to bypass through the tool and pass out into the zone above through the ports 50 in the upper body.

Near the upper end of the control mandrel 52 is a transverse bar 74 which is suitably afiixed to the mandrel. The bar 74 extends diametrically through the upper end of the tool and passes radially through slots 76 formed in a rotatable section 78, which constitutes a part of the upper body 10. More particularly, the rotatable section 78 of the upper body is mounted in a fixed position longitudinally of the main part 14 of the upper body, by virtue of a circumferential flange and slot-formation 80 between the upper end of the main section 14 and the lower end of the rotatable section 78. However, the rotatable section 78 is mounted for clockwise rotation relative to the main section 14. Accordingly, the control mandrel 52, which is otherwise free of any restrictions against rotation relative to the upper and lower bodies of the tool, may be rotated clockwise (to 8 the right) while the main section 14 of the upper body and the lower body 12, as well as all other parts of the tool, remain stationary.

Referring briefly to FIG. 5, counterclockwise (left) rotation of the control mandrel 52 and of the rotatable section 78, relative to the main section 14 of the upper body 10, is precluded by a clutch arrangement which comprises a clutch piece 82 carried in a slot 84 formed in the upper end of the main section 14 of the upper body and spring-loaded outwardly by spring 86 to en gage cam teeth 88 on the clutch piece with companion teeth 90 formed on the inner wall of the rotatable section 78 of the upper body 10. As will be readily apparent from consideration of FIG. 5, rotation of the control mandrel clockwise relative to the main section 14 causes the rotatable section to ratchet past the clutch piece 82, which is urged in against its spring 84 and permits a clockwise rotation of the rotatable section. However, a force tending to turn the rotatable section 78 to the left (counterclockwise) brings the generally radially disposed walls of the teeth into engagement and locks the section 78 against rotation relative to the main section 14 of the upper body 10'.

The retrievable bridge plug is run down into the casing C by pushing it down with a tubing string tool or a weighted wire line running tool. In either case, one form of running tool, which is not shown in the drawings, may be composed of a sleeve portion which fits down over the upper end of the tool and a head portion which is appropriately formed so as to bear against the toppiece of the control mandrel head 54 and thereby impart a downward force on the control mandrel. The running tool need not have any slot arrangement on it," although a slotted tool, such as the one described below and shown in the drawings, may be used with tubing so that operations involving the tubing may-be performed above the bridge plug, while the bridge plug is released and anchored, and the running tool may then be used to retrieve the tool without the need for removing the tubing from the well. In a tubing operation, the string of tubing may include a. well packer, and the running tool will be attached into the tubing string below the well packer. In either case, the lowering of the retrievable bridge plug down into the casing is accomplished by imposing a downward force on the control mandrel 52.

It will be recalled that, as far as the tool has been described thus far, the lower body is freely movable relative to the upper body between upper and lower limit positions established by the upper and lower shoulders 32 and 30,v respectively, in the enlargedinterior wall portion 28 of the upper body. However, the retrievable bridge plug, as exemplified by the embodiment illustrated in the drawings, includes a latch arrangement for locking the upper and lower bodies together in their positions of greatest extension, relative to each other, so that the bridge plug can be latched in its running in and retrieving position, i.e., its unset position, with the slips retracted inwardly.

More particularly, the latch arrangement comprises an indentation or notch 90 in the outer wall of the lower body at a point below, but in proximity to, one of the drag shoes 22 carried by the upper body. A latch element 92 is mounted for pivotal movement about a pivot pin '94, which is disposed generally tangentially to the tool. A projection 96 on the latch element extends into the notch 90 when the latch dog 92 is pivoted about its mounting pin 94 so as to move the projection 96 radially inwardly. Referring briefly to FIG. 4, the latch dog 92 is pivoted in such direction by engagement of a flange portion 98 on it by a companion flange 100 formed on the drag shoe 22 when the drag shoe 22 is urged outwardly into its radially outermost position by its springs 24. Accordingly, the upper body is held in fixed position relative to the lower body whenever the friction drag shoe 22 is in its outermost position. It may be mentioned here that it may be desirable to provide a latch piece 92 and companion notch 90- in association with each of the drag shoes 22 of the tool.

Although the latch arrangement facilitates handling the tool when it is out of the well, such as during maintenance, transportation and rigging for an operation, it is particularly useful in the operation of inserting the tool into the casings. FIG. 3 depicts the tool in a position in which it has been partially inserted into the casing to an extent that the drag shoes 42 on the lower body are fully in the casing. Beginning at the point when the lower packing cup enters the casing, the lower body and the parts carried by it resist downward movement and the lower body must thereafter be pushed down through the well. Inasmuch as the upper drag blocks 22 are in their outermost extended position at this time, that is, so long as the drag block is not pushed inwardly as it is when it enters the casing, the latch piece 92 is in the latched position, as best shown in FIG. 4, and the upper body cannot move downwardly relative to the lower body with the result that the slips would be pushed out into engagement with the casing C. Consequently the tool is readily introduced into the well.

As soon as the drag shoes 22 on the upper body 10 move into the casing and are thereupon pushed radially inwardly, the companion flanges 98 and 100 on the drag shoe 22 and the latch piece 92 are removed from engagement so that the latch can relatively freely pivot in a direction to remove the projection 96 from the notch 90. As best shown in FIG. 4, the longitudinal ends of the notch 90 are tapered away from the base of the notch so that at such time as the upper body may be shifted downwardly relative to the lower body, which will generally not take place until the tool is to be set in the well casing after being lowered into proper position, the latch dog is cammed outwardly and the projection rides out onto the cylindrical surface of the lower body section 38 below the notch 90 It should be clear from the above description that the latch will automatically be restored to its latched condition when the tool is removed from the well. In this regard, as will be described in more detail below, the tool is removed from the well by pulling upwardly on the control mandrel, which in turn pulls on the upper body, and the upper body then pulls the lower body up with it. Consequently, the upper body will be in its uppermost position relative to the lower body, which corresponds to the latched position shown in FIGS. 3 and 4. As soon as the tool has been pulled out of the casing to an extent that the drag shoe 22 on the upper body is no longer confined by the casing but moves to its outward-most position, the latch projection is pushed back into the companion notch on the lower body to lock the tool in the unset position.

The frictional .forces developed by parts of the retrievable bridge plug that engage the casing wall, principally the drag shoes on the upper and lower bodies but also the packing elements, will support the upper and lower bodies (and the parts carried by them) independently of each other in the casing against movement in either direction. In other words, neither the upper body nor the lower body will move relative to the other, absent the development of a changed pressure condition tending to force one or the other bodies towards the other. Accordingly, movement of the tool either up or down in the casing involves pulling the control rod up or pushing it down.

FIGS. 1A, 1B and 1C show the tool in the running-1n position. It will be understood that the running-in tool is arranged so that it imposes a downward force on the top piece 54 of the control mandrel. Such a downward force on the control mandrel moves the control mandrel down against the resisting force of the spring 59 associated with the lower valve 58 and brings the lugs 62 on the lower valve into bearing engagement against the shoulder 64 on the lower body and imposes a downward force on the lower body and pushes the lower body down through the well against the resisting forces developed by the low drag shoes 42 and lower packer. Meanwhile, the drag shoes 22 and the upper packing element 34 associated with the upper body 10 resist the downward movement of the upper body so that the lower shoulder on the enlarged part 36 of the lower body is brought into engagement with the lower shoulder 30 on the enlarged internal wall portion 28 of the upper body (see FIG. 1B). Thus, the downward force on the control mandrel is also imparted to the upper body so that the upper body is pulled downwardly along with the lower body. However, the upper body and lower body are in their positions most remote from each other so that the slips remain in retracted position, as shown in FIG. 1C. Meanwhile, the lower valve is held open by engagement of the flange 56 on the control mandrel so that well fluids can pass in though the port 48 at the lower end of the lower body, up through the central bore 46 through the tool, past the open lower valve 58 and, by virtue of the pressure force which forces the upper valve 68 to open against its spring, through the upper valve and out through the upper ports 50 into the zone above the tool, thereby by-passing well fluids relatively freely as the retrievable bridge plug is pushed down into the casing.

As the tool is lowered to the well and the ambient fluid pressure has increased, there might be a tendency, if it were not for the following feature of the retrievable bridge plug, for the annular space between the bridge plug and the casing and confined longitudinally by the upper and lower packing cups to trap a relatively low pressure so that there would be a rather large differential pressure across the two packing cups. However, the upper body of the tool is provided with a bleeder port 102 communicating the part of the center passage 46 between the valves 58 and 68 with the aforementioned annular space. Consequently, the annular space will be kept at substantially the ambient pressures whenever the tool is being moved through the well.

When the retrievable bridge plug has been moved down to a desired position where it is to be set, it may be released from the running tool by simply pulling the running tool upwardly, thus leaving the retrievable bridge plug in place. Where a J-slot type running tool is used, as will be described below, appropriate manipulation of the tubing string is accomplished to release it from the control mandrel.

At any time that a downward or upward force is removed from the control mandrel, the springs 59 and 70 associated with the valves shift the mandrel into a neutral position in which both of the valves are urged in the closed positions, and therefore the passage of fluids in either direction around or through the retrievable bridge plug is thereafter precluded.

When a pressure differential is established, for one reason or another, between the Zone below the tool and the zone above it, the tool automatically becomes anchored in the well casing again t movement in either direction, and also seals or bridges the casing against passage of fluid or communication of fluid pressure across the tool. More particularly, assuming that an operation is being performed in which the fluid pressure above the tool is higher than the fluid pressure below it, a net downward force due to pressure is exerted on the upper body through the upper packing cup and upper valve and pushes the upper body downwardly. Meanwhile, the lower body is held in position in the casing by the lower drag shoes, assisted to some degree by the frictional forces developed by the lower packing cup 44, and therefore the upper body moves downwardly relative to the lower body. This causes the expander surfaces 16 at the lower end of the upper body to slide downwardly along the slips 18 and to expand the slips outwardly into gripping 1 1 engagement with the ca ing C. The teeth on the slips 18 grip and dig into the well casing, and even the development of very high differential pressures across the tool only serves to set the slips more firmly.

If the operations performed with the tool in the well are such that a greater pressure is established below the retrievable bridge plug than above it, the retrievable bridge plug will become anchored against upward movement. Again, the net force due to the differential pressure, which acts on the lower packing and valve and other downwardly facing parts of the tool, shift the-lower body upwardly while the upper body is held in position in the casing by its drag shoes 22 and the upper packing cup- 34. Accordingly, the lips move up along the expander and are pushed outwardly into engagement with the casing. However, to the extent that the tool has been described thus far, there is no significant reaction force acting downwardly on the expander to resist the sliding movement of the expander and slips upwardly. However, the retrievable bridge plug provides for the generation of a hydraulic reaction force acting down on the expander so that even though the net forces due to pressure acting on the lips 18 to force them up are otherwise not adapted to provide firm anchoring of the tool in the casing, the hydraulic reaction forces on the expander creates the required wedging action to ensure that the tool will be firmly anchored to the casing against upward movement.

More particularly, the upper end of the lower body 12 is sealed to the lower body, such as by O-rings 104- and 106 (see FIG. 1B or 2B), so as to close off a chamber (see particularly FIG. 2B) defined by the lower part of the enlarged inner surface portion 28 of the upper body and the outwardly facing portion of the lower body oppo ite the aforementioned wall portion, and by the upwardly facing shoulder 30 on the lower body and the downwardly facing shoulder, designated by the reference numeral 36a, on the enlarged portion 36 at the upper end of the lower body. The fluid pressure chamber 103 is of variable volume, by virtue of the relative movement between the upper body and lower body and is in communication with, and therefore at substantially the same pressure as, the zone of the well below the retrievable bridge plug by reason of a port 108 communicating with the central passage of the tool at a point below the lower valve element 58.

Considering a projected area A in a radial plane of the tool defined by the sealing points of the seals 104 and 106 and between the upper and lower bodies, the upwardly facing surface of the lower body, namely, the shoulder 30, is acted upon by the higher pressure below the tool (under the conditions being considered here) while the downwardly facing surfaces in the projected area A are exposed to the pressure in the annular space between the outside of the retrievable bridge plug and the casing and longitudinally between the two packing elements. A has been described previously, the fluid pressure in such annular space will tend to be substantially the same as that in the lower pressure zone, and when the pressure below is higher than the pressure above the retrievable bridge plug, the annular space will tend to be close to the lower pressure above the upper packing cup, inasmuch as fluid will bleed off past the upper packing cup. Inasmuch as the upper body has surfaces in the projected area A which are subject to different fluid pressures, a net downward force due to a pressure is exerted on the upper body and provides a reaction force urging the expander 16 down under the slips and therefore firmly anchors the slips and holds the tool against upward movement.

Although the above description has proceeded on the assumption that the tool was not previously set when a differential pressure was created across it, it will be entirely clear to those skilled in the art that a shift in pressure conditions so that the slips must hold in a direction opposite from that in which they were holding when the tool originally became set will not result in any move- 12 ment of the tool and will merely modify the precise way in which the active forces are generated and transmitted into the casing through the parts of the tool. Therefore, it does not seem necessary to describe this aspect of the operation of the tool here.

The retrievable bridge plug is released from anchored and sealed condition in the casing by connecting a suitable retrieving tool to the controlled mandrel. Various forms of retrieving tools can be used, but in many operations in which the retrievable bridge plug is used, solid materials, such as sand or mud, may accumulate on top of the retrievable bridge plug and will require washing down to the tool before the retrieving tool can be connected to it. Accordingly, a tubing type of retrieving tool, preferably one with milling teeth to facilitate washing down through the solid material, will often be used. However, where the operation was such as to not require washing down to pick up the retrievable bridge plug, a wire line retrieving tool having a relatively simple J-slot arrangement can be used.

FIGS. 6 and 7 show an exemplary embodiment of a suitable tubing-type retrieving tool 110 which, however, can also be used to lower the retrievable bridge plug into the well. The retrieving tool 110 comprises a head portion 112 which is threaded onto a length of tubing or onto the lower end of another tool, such as a well packer, and a cylindrical sleeve 114 which, as shown in FIG. 3, fits down over the top portion of the retrievable bridge plug. Within the sleeve are two identical slot formations 116 which are apart and, as shown in FIG. 7, include inclined portions 116a opening at the lower end of the sleeve and extending at an angle upwardly to the center part of longitudinal slot portions 1161). The respective slot forrnations receive one end of the transverse bar 74 on the control mandrel. As the retrieving tool 110 is lowered down over the upper end of the retrievable bridge plug, the J-slot formations guide it down automatically to locate the ends of the transverse bar 74 in longitudinal slot portions 116]). By pulling up on the retrieving tool, the transverse piece 74 is located in the lower end of the longitudinal portions and thus enables an upward force to be imparted to the control mandrel.

Preferably, an up and down movement of the retrieving tool should be the first step in releasing the retrievable bridge plug from the casing. Such up and down movements will ensure that both valves are opened and that any differential pressure across the retrievable bridge plug is equalized. The retrievable bridge plug is then released from anchored condition by pulling up on the control mandrel. An upward movement of the control mandrel brings the transverse bar 74 on the control mandrel into engagement with the upper ends of the slots 76 in the upper section of the upper body and enables the further upward movement of the mandrel to pull the upper body away from the lower body so that the expander surfaces are pulled out from under the slips and the slips are brought into their retracted positions.

Once the retrievable bridge plug has been released from its anchored condition in the well, it may be moved either up or down to another location or it may be pulled up and removed entirely from the well casing. If the retrievable bridge plug is to be moved to another location, it may be released and reset, in the manner as described above, and such re-use for operations in the well at different locations may take place as often as necessary or desired. The retrievable bridge plug may, of course, be kept in the well for extended periods of time, if desired or necessary or it may be retrieved immediately.

The embodiment of the invention described above is intended to be merely exemplary, and those skilled in the art will be able to make numerous variations and modifications of it without departing from the spirit and scope of the invention.

I claim:

1. A well packer comprising :an upper body and a lower body adapted to be lowered into a well conduit, the lower body depending from the upper body and joined to the upper body for limited sliding movement longitudinally relative thereto, an upwardly facing cup-type packing element on the upper body adapted to form a seal between the upper body and the well bore wall .against downward passage of well fluids, a downwardly facing cup-type packing element on the lower body adapted to form a seal between the lower body and the well bore wall against upward passage of well fluids, slip means mounted on the lower body for movement therewith relative to the upper body and shiftable outwardly into anchoring engagement with the well conduit wall, expander means on the upper body to urge the slip means outwardly upon upward movement of the lower body relative to the upper body, fluid pressure means including a fluid chamber of variable volume defined by wall formations associated with the upper body and the lower body and responsive to a greater pressure below the downwardly facing packing element than above it for urging the upper body downwardly and thereby urging the expander toward the slip means, and control means for selectively permitting or preventing movement of the upper body relative to the lower body.

2. A well tool according to claim 1 wherein the upper and lower bodies are in telescoping relation and the fluid chamber is located in overlapping parts of the bodies.

3. A well tool according to claim 2 wherein the interior of the chamber communicates with a zone of the well below the lower packing element and the exterior of the chamber communicates With a zone above the lower packing element.

4. A well tool according to claim 1 further comprising a passage through the body communicating the parts of the well bore above and below the packing elements with each other, and valve means in the passage and operable by the control means to selectively close olf the passage to prevent communication of well fluids between the said zones.

5. A well tool according to claim 1 wherein the control means includes means for selectively (a) imposing a downward force on the lower body preventing movement of the slip means relative to the body, and (b) imposing an upward force on the upper body.

6. A well tool according to claim 5 wherein the control means further includes friction drag means associated with the upper body and engageable with the well conduit to impede movement of the upper body through the conduit, and friction drag means associated with the lower body to impede movement of the lower body through the conduit.

7. A well tool according to claim 5 wherein the control means includes a member shiftable longitudinally of the bodies and elements coupled to the member and selectively engageable in different positions of the member relative to the bodies with (a) the upper body and (b) the lower body to maintain the bodies in selected positions relative to each other.

8. A well tool according to claim 1 further comprising latch means associated with the bodies for selectively latching them together against relative shifting and releasable to permit such relative smifting.

9. A well tool according to claim 8 wherein the latch means is normally latched when the well tool is not in a well conduit and automatically releases upon introduction of the tool into a well conduit.

10. A well tool according to claim 9 wherein the latch means includes a latch piece movably mounted on the upper body and having a projection thereon, a notch formed on the lower body in a location to receive the said projection and means associated with the member for selectively moving it to shift the projection in and out of the notch.

11. A well tool according to claim 10 further comprising a friction drag shoe carried by the upper body and resiliently urged outwardly, and wherein the means for moving the latch piece includes a formation on the friction drag shoe.

12. A well tool according to claim 11 wherein the latch piece is pivotly mounted on the body adjacent the friction drag shoe and has a portion on one side of the pivot axis engaged by the said formation of the drag shoe and wherein the projection on the latch piece is on the other side of the pivot axis, the projection normally being urged into the notch on the lower body when the drag shoe is urged into its outermost position on the body and being released from engagement with the notch when the drag shoe is displaced inwardly from the said outermost position.

13. A well tool according to claim 7 further comprising a rotatable body member mounted on the upper body for rotation relative thereto while fixed longitudinally thereon, and wherein the element of the control means which is engageable with the upper body engages the upper body through the rotatable body member.

14. A well tool according to claim 13 .further comprising clutch means between the rotatable-member and the upper body for permitting rotation of the rotatable member relative to the body in one direction only.

15. A well packer comprising an upper body and a lower body adapted to be lowered into a well conduit, the lower body depending from the upper body and joined to the upper body for limited sliding movement longitudinally relative thereto, friction drag means associated with the upper [body and engageable with the well conduit to impede movement of the upper body through the conduit, friction drag means associated with the lower body to impede movement of the lower body through the con duit, an upwardly facing cup-type packing element on the upper body adapted to form a seal between the upper body and the well bore wall against downward passage of well fluids, a downwardly facing cup-type packing element on the lower body adapted to form a seal between the lower body and the well bore wall against upward passage of well fluids, a passage through the body communicating the parts of the well bore above and below the packing elements with each other, valve means in the passage shiftable selectively to close off the passage to prevent communication of well fluids between the said zones or to open said passage and permit such communication, slip means mounted on the lower body for movement therewith relative to the upper body and shiftable outwardly into anchoring engagement with the well conduit wall, expander means on the upper body to urge the slip means outwardly upon upward movement of the lower body relative to the upper body, fluid pressure means including a fluid chamber of variable volume defined by wall forma tions associated with the upper body and the lower body and responsive to a greater pressure below the downwardly facing packing element than above it for urging the upper body downwardly and thereby urging the expander toward the slip means, and control means for selectively permitting or preventing movement of the upper body relative to the lower body and for operating the valve means.

16. A well tool according to claim 15 wherein the interior of the chamber communicates with a zone of the well below the lower packing element and the exterior of the chamber communicates with a zone above the lower packing element.

17. A well tool according to claim 15 wherein the control means includes means for selectively (a) imposing a downward force on the lower body preventing movement of the slip means relative to the body, and (b) imposing an upward force on the upper body.

18. A well tool according to claim 15 wherein the valve means includes a lower valve element spring-loaded upwardly to a closed position seating on a seat on the lower body and an upper valve element spring-loaded downwardly to a closed position seating on a seat on the upper body.

19. A well tool according to claim 18 wherein the control means includes a member shiftable downwardly 15 to (a) engage the lower valve' toopen it and to (b') simultaneously impose a downward force on the lower body and shiftable upwardly to (a) engage the upper valve to open it and to (b) simultaneously impose an upward force on the upper body.

20. A well tool according to claim 15 further comprising latch means associated with the bodies for selec-' tively latching them together against relative shifting and releasable to permit such relative shifting.

21. A well tool according to'claim 19 wherein the latch means is normally latched when the well tool is not in a well conduit and automatically releases upon introduction of the tool into a well conduit.

22. A well tool according to claim 20 wherein the latch means includes a latch piece movably mounted on the upper body and having a projection thereon, a notch formed on the lower body in a location to receive the said projection and means associated with the member for selectively moving it to shift the projection in and out of the notch.

23. A well tool according to claim 21 wherein the means for moving the latch piece includes a formation on a friction drag shoe.

24. A well tool according to claim 22 wherein the latch piece is pivotly mounted on the upper body adjacent a friction drag shoe and has a portion on one side of the pivot axis engaged by the said formation of the drag shoe and wherein the projection on the latch piece is on the other side of the pivot axis, the projection normally being urged into the notch on the lower body with the upper body engages the upper body through the rotatable body member.

26. A well tool according to claim 24 further comprising clutch means between the rotatable member and the upper body for permitting rotation of the rotatable member relative to the body in one direction only.

References Cited UNITED STATES PATENTS 2,585,706

2/1952 Ware 166l21 X 3,050,128 8/1962 Brown 166l34 3,314,480 4/1967 Scott 166l33 3,357,493 12/1967 Conrad 166133 3,361,207 1/1968 Chenoweth 166--120 JAMES A. LEPPINK, Primary Examiner US. 01. X.R. 166 133, 134 

